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Adding 9, 19 and 99 Mental Maths Worksheet

Mental maths lesson 4: Add and take away 9, 19 and 99 · Set 220 · 40 questions
TalentJR

How to do it in your head (Round and adjust): Add 9, 19, 99: add 10, 20, 100, then take 1 away. Take away 9, 19, 99: take away 10, 20, 100, then add 1 back. Ask yourself: did I use too much or too little?

NameDateTime takenScore ___ / 40
  1. 1.55 + 9 =
  2. 2.30 + 19 =
  3. 3.234 + 99 =
  4. 4.380 − 99 =
  5. 5.53 + 9 =
  6. 6.716 − 99 =
  7. 7.46 + 9 =
  8. 8.77 − 29 =
  9. 9.71 − 9 =
  10. 10.272 + 99 =
  11. 11.540 − 99 =
  12. 12.33 − 19 =
  13. 13.63 − 19 =
  14. 14.69 + 9 =
  15. 15.67 + 29 =
  16. 16.71 + 19 =
  17. 17.29 + 19 =
  18. 18.45 − 19 =
  19. 19.547 + 99 =
  20. 20.32 − 19 =
  21. 21.49 + 29 =
  22. 22.60 − 9 =
  23. 23.99 − 29 =
  24. 24.19 + 9 =
  25. 25.67 + 9 =
  26. 26.323 + 99 =
  27. 27.540 + 99 =
  28. 28.15 + 19 =
  29. 29.56 + 9 =
  30. 30.85 − 9 =
  31. 31.47 − 19 =
  32. 32.817 − 99 =
  33. 33.38 − 9 =
  34. 34.43 + 9 =
  35. 35.24 + 9 =
  36. 36.342 − 99 =
  37. 37.37 + 9 =
  38. 38.26 + 19 =
  39. 39.12 + 29 =
  40. 40.38 + 9 =

Answer key

  1. 64
  2. 49
  3. 333
  4. 281
  5. 62
  6. 617
  7. 55
  8. 48
  9. 62
  10. 371
  11. 441
  12. 14
  13. 44
  14. 78
  15. 96
  16. 90
  17. 48
  18. 26
  19. 646
  20. 13
  21. 78
  22. 51
  23. 70
  24. 28
  25. 76
  26. 422
  27. 639
  28. 34
  29. 65
  30. 76
  31. 28
  32. 718
  33. 29
  34. 52
  35. 33
  36. 243
  37. 46
  38. 45
  39. 41
  40. 47

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